The present invention relates to prostheses and more particularly to artificial limbs having means for supporting the terminus or stump of an amputated body member.
Artificial limbs are usually provided with a socket into which the amputated end of a body member is inserted. Such stump-receiving sockets normally perform a number of critical functions. For example, one important socket function, especially if the limb is an artificial leg, is providing a weight-bearing surface for the stump. Another important socket function is supplying lateral support to the sump to maintain stability for the wearer. Other typical functions of a socket include attaching the artificial limb to the wearer and maintaining mechanical freedom of motion for a joint such as a knee, or the like.
One of the most critical problems confronting developers of such limbs has been the reduction of unwanted pressures on critical anatomical portions of the stump, such as bones, nerves, veins, arteries, ligaments, tendons, and the like. When the prosthesis is an artificial leg, the weight-bearing characteristics of the stump-supporting socket become a critical consideration. This is so because the required support and stability must be accomplished without causing undesirable pressures at those critical anatomical points on the stump, i.e., veins, ligaments, nerves, bones, etc. It is equally important, however, that there be a relatively uniform surface over the area of contact between the prosthesis and the stump. It has been found that significant abrasions of the skin often occur at those areas where movement and rubbing occurs between the skin and the supporting surfaces.
In the past, prosthesis devices have been proposed which include inflatable collars, bags, membranes, etc. that seat in or around the usual stump-receiving socket for the purpose of providing a cushioned support for the stump. Such devices have not been entirely satisfactory in that either the weight-bearing surface is unduly small, thereby creating large forces at the supporting surfaces, or the inflatable supports completely encircle the stump, thereby causing pressures and constricting forces at undesirable points, or there are unacceptable numbers of discontinuities in the support surface, thereby creating areas of potential skin abrasions. Additionally, it has also been typical for the collar, bag or membrane to have a single inflatable chamber thereby causing instabilities due to undamped motions when in dynamic use. These problems are overcome by the present invention.